Dietary oak ( Quercus brantii ) acorn extract affects growth performance, survival rate, haemolymph parameters, and body composition of narrow‐clawed crayfish ( Pontastacus leptodactylus )

Abstract

Herbal extracts have been successfully utilized to improve the growth, survival, immunity, and disease resistance of aquatic animals. The present experiment was designed to investigate the effects of dietary acorn extract on growth, survival rate, proximate composition, and haemolymph parameters of narrow-clawed crayfish (Pontastacus leptodactylus). A total number of 360 crayfish (39.17 +/- 0.73 g) were randomly distributed into four treatments and fed experimental diets containing 0 (control), 0.5, 1, and 2 g/kg diet of acorn extract for 90 days. The results showed significant improvement in all growth parameters, weight gain ratio (WGR), specific growth rate (SGR), food conversion ratio (FCR), and protein efficiency ratio (PER), as well as survival rate between acorn extract, supplemented crayfish and control with the maximum performance in the 2 g/kg diet of acorn extract (p < 0.05). The dietary acorn extract increased the concentration of total protein, glucose, cholesterol, potassium (K), and calcium (Ca) (p < 0.05). Hepatic enzymes, including alkaline phosphatase (ALP), lactate dehydrogenase (LDH), serum glutamic oxaloacetic transaminase (SGOT), and serum glutamic pyruvic transaminase (SGPT), were not affected by dietary acorn extract (p > 0.05), suggesting no toxic effect on the hepatopancreas. Moreover, animals fed on dietary acorn extract had higher crude protein and lower crude lipid contents compared to the control group (p < 0.05). In conclusion, our findings revealed that feeding P. leptodactylus with acorn extract at 2 g/kg level significantly improves the growth performance and survival rate, without negative impacts on the health status.